We plan to continue the study of the role of steroids in the lumena of the reproductive duct system. Do they aid in motility of the duct system? (sperm travel? Ova transport?); are they necessary for implantation in animals other than the rat? or, is the duct system a means of disposing of steroids not needed by the body? Further comparisons will be made between the size of follicle (antrum versus without) and their steroidogenic competency. In adult rabbits, veins of both ovaries will be cannulated and control samples taken. In one ovary all large tertiary preovulatory follicles will be cauterized and blood sampled. LH will be injected and again blood from both ovaries will be sampled and analyzed for steroid concentration. An attempt will be made to disentangle the question concerning steroid synthesis versus release and of the role of the steroids stored in the follicular fluid. Labelled steroid (probably E2) will be injected directly into the follicle lumen followed by systemic LH injection. The ratio of cold versus hot steroid in the ovarian effluent blood will be measured. Bibliographic references: Foxcroft, G. R., D. K. Pomerantz, and A. V. Nalbandov. 1975. Effects of estradiol-17 beta on LH-RH/FSH-RH-induced, and spontaneous, LH releases in prepubertal female pigs. Endocrinology 96:551-557. Pomerantz, D. K., G. R. Foxcroft, and A. V. Nalbandov. 1975. Acute and cronic estradiol-17 beta inhibition of LH release in prepubertal female pigs: Time course and site of action. Endocrinology 96:558-563.